wood pigeon in a java dove nest

[sueUK]

Hi - I'm from the UK and I've had pet Java doves for a couple of years.
I am now down to one very tame female, who has a big cage in my kitchen. She laid two eggs a few weeks ago, and I was sad for her knowing they were infertile and could never hatch.
Anyhow - when she's been faithfully sitting for nearly 3 weeks, and I was deciding to throw the eggs out before she made herself ill - lo and behold, my old grey cat comes in one night, makes a weird growling noise, and very carefully deposits a small white egg on the kitchen mat. He then loses interest in it totally and wondered off!
I picked the egg up in utter amazement - no cat has ever brought an egg in before - mice, birds, frogs and even snakes, but never an egg!
The egg was completely unharmed, and warm.
You guessed what I did then. I did what any other mad person would do - I chucked out one of the 'dud' eggs from under Georgie the dove, and popped this new one in under her.
Less than a week later the new little egg hatched. My teenage son noticed the activity, and we got very excited! Eventually a chick was hatched, and we identified it as a wild wood pigeon! Georgie is thrilled to bits!
Georgie has no crop milk - I assume because the timing was all wrong in relation to her own eggs, so I am feeding this wee scrap of pigeon, and Georgie is keeping it warm and safe under her. She clucks and coos and wiggles her wings, and seems utterly taken with her baby.
5 times a day I lift baby out on his little piece of paper towel, feed him a lovely gooey mix whos recipe I found on the internet, clean him up, put him on a fresh kitchen towel, and back into his little basket that serves for a nest. Georgie doesn't seem to mind me taking him away, but she's always pleased when I put him back.
He is now 3 days and 6 hours old. He is growing well - I still have his egg, and no way would he ever get back in it now!! but as each day goes by I get more anxious about the possibility of him dying. At first it was "I have to try, hope for the best" but now its more like "But he's our baby!"
I need to know if there's anything I haven't thought of, and we want a name for him/her, and if he survives - what do we do with him???
Has anyone else come accross such a strange incident? I wonder if God just REALLY wants me to rear a baby pigeon for some reason!
Sue